1. Field of the Invention
This invention relates to a lens barrel to be used for a camera or the like.
2. Description of the Related Art
FIGS. 7 and 8 of the accompanying drawings show by way of example the conventional lens barrel adapted for a video camera. These illustrations include a lens barrel body 110; an iris galvanometer (IG meter) 112 which is arranged to drive an iris; a zooming motor 114; a reducing transmission system 115 which is arranged to reduce the output of the zooming motor 114 and to rotatively drive a zoom ring 117 to perform a zooming action; and a focusing motor 116 which is arranged to perform a focusing action by rotatively driving a distance ring 119 through a reducing transmission system similar to the reducing transmission system 115 which is provided for zooming. Circuit elements which are not shown in detail are arranged on a printed circuit board 118. A distance measuring device 120 is of the active type. Although it is not shown, a printed circuit board having a large area is arranged within the lens barrel in a manner as disclosed in U.S. patent application Ser. No. 136,346 filed on Dec. 22, 1987.
Electrical elements such as a CCD, etc., that are apt to be affected by noises have recently come to be incorporated in the camera body of a video camera or the like. For the video camera of this kind, if the zooming motor 114 and the focusing motor 116 are disposed at the rear end of the optical axis (closest to the camera body) like the conventional lens barrel, the electrical elements such as a CCD, etc., would be affected by noises produced by the motors 114 and 116.
Further, if three drive sources (for aperture, zooming and focusing) are included within the lens barrel, like in the case of a video camera, the lens barrel would be greatly deformed from the cylindrical external shape of the above-stated example of the conventional lens barrel. This not only increases restrictions imposed on the design of the lens barrel but also deteriorates the mounting and dismounting operability of the lens barrel in cases where the lens is arranged to be interchangeable.